I'm running on Ubuntu 7.04, using Java 1.6.0_02, and mercurial 0.9.4 built from source.  In order to ensure I was
starting from a fresh state, I extracted a new copy of the zipped NetBeans 6 beta1 JavaSE distribution and deleted my
~/.netbeans folder.  After launching, I installed the mercurial plugin from the update center, then restarted the IDE
when prompted.

I created a new Java appliction, accepting all the defaults.  I initialized the hg repository from the Versioning menu,
then did my initial commit.  Next I deleted Main.java from my project, and commited again. So far so good.

I added a new java class to my project, and attempted to commit again.  The commit dialog correctly listed NewClass.java
as being Locally Added, but still included Main.java as Locally Removed, despite the fact that it was deleted on the
previous commit.  Attempting to commit anyway gave me the error "unable to execute hg command".

If I exclude the file from the commit all works well, but it continues to show up in commit and status dialogs until I
delete ~/.netbeans/6.0Beta1/var/cache/mercurialcache and restart netbeans.  Things are fine after that, until I delete
another file.